Preliminary evidence suggests that there is a difference in the vasoactive response in the coronary arteries of miniswine to various pharmacologic agents. Significant changes can be observed with thromboxane like drugs, histamine, ergonovine maleate, and acetylcholine. Hyperlipidemia and/or atherosclerosis in coronary vessels of miniswine alter the normal vasodilating response to histamine. Acetylcholine may have a potentiated vasoconstricting effect on atherosclerotic vessels but not necessarily in all hyperlipidemic animals. Finally, the response of the coronary vessel to various receptor mediated agonists is highly heterogeneous between animals, even those that are genetically similar. In-vitro coronary vessels preparations do not necessarily correlate with results derived from in-vivo preparations. Histamine and acetylcholine responses are diametrically opposed to those seen in the intact animal. Furthermore, in-vitro contractile responses to histamine are different in the right coronary artery, vs the two left coronary vessels. Isolated muscular preparations of coronary vessels also appear to be affected by low density lipoprotein in the bath solution. A plasma two-dimensional gel system has been completed to elucidate apolipoprotein changes in miniswine with feeding, as well as genetic defects in the human apolipoproteins. These alterations in apolipoproteins with high fat feeding in miniswine correlate with the resulting hyper and hyporesponder defined by plasma cholesterol concentrations.